Method of bending tubes and machine therefor



s. WILMAN METHOD OF BENDING TUBES AND MACHINE THEREFOR Filed Dec. 18, 1962 4 Sheets-Sheet 2 METHOD OF BENDING TUBES AND MACHINE THEREFOR Filed Dec. 18, 1962 S. WILMAN Dec. 12, 1967 4 Sheets-Sheet 3 INVENTOR SlGISMOND WI'LMAN 'By 'fM ATTORNEY;

1967 s. WILMAN 3,357,221

METHOD OF BENDING TUBES AND MACHINE THEREFOR Filed Dec. 18, 1962 4 SheetsSheet 4 78 72 53 54 56 a I I I 6 58 7 72 75 77 74 59 Z 40 57 6 61 70 60 1 I I m 68' 66 66 68 5 V 67 as INVENTOH SiGISMCND WILMAN 'BH MQWM ATTORNEYS United States Patent Ofiice 3,357,221 Fatented Dec. 12, 1E5? 3,357,221 METHOD OF BENDING TUBES AND MAC TIEREFOR Sigismund Wilman, 1-3 Rue dEvreux, Courbevoie, France Filed Dec. 18, 1962, Ser. No. 245,460 Claims priority, application France, Oct. 1, 1962, 910,914; Dec. 5, 1962, 917,595 1 Claim. (Cl. 72--69) The method of bending tubes under heat is well known, as are also the drawbacks involved therein, the chief one being the obligation to fill the tube with sand, to make it red-hot and then bend it, which is a very costly process.

Likewise known is the tube bending method involving rolling the walls about an axis offset relative to the tube axis, in order to reduce the thickness of the tube wall on the side of the outer arc of curvature, without the thickness on the opposite side being substantially changed. Although the latter method is more economical than the former, it causes greater thinning down of the Wall on the outer arc of curvature, which is often criticized.

The method according to this invention embodies all the advantages of these two methods yet eliminates the drawbacks referred to. It consists basically in producing an elongation by cold thinning of the tube, on the side of the outer arc of curvature of the wall, preferably only over a portion which is somewhat less than half the tube periphery (say over 160), and in heating up the opposite portion designed to form the inner arc of curvature, likewise over about 150 to 160", the neutral fibers over a small width on both sides of the tube being neither heated. nor thinned down.

In this way, the elongation due to the thinning down of the metal over the outer arc produces a tension capable of compressing the metal on the opposite side of the neutral plane, provided that the temperature rise is adequate to make the metal ductile and easy to compress; in the case of steel, for example, the temperature rise can be to about 1000 to 1100 C. When this is the case, compression of the heated portion will be effected with a minimum of efiort, solely due to the elongation of the wall .over the outer arc. The wall can be thinned down by suitably operating thereon, either from within the tube when large diameter tubes are involved, or from without in the .case of smaller diameters.

The machine adapted to accomplish this initial thinning down from the interior is provided with a rolling head of a known type, comprising for instance a rolling wheel and two thrust wheels, or else two rolling wheels and one thrust wheel. The motion of the rolling head is preferably oscillatory along a circular arc of less than 180, in order to avoid rolling the heated portion which, onthe contrary, must be compressed. On the other hand, the machine adapted to effect the thinning down from the exterior can be provided either with external rolling devices such as balls, rollers, or the like, or with wall thin .ning devices operating by successive pressures exerted at regular intervals, or by hammering.

The description of a few possible embodiments of the present invention, given with reference to the accompanying drawing which is filed by way of example only I and not of limitation, will give a clear understanding of how the invention can be carried into effect. Referring to the drawing filed herewith:

FIGURE 1 is a longitudinal sectional view of the front and rear extremities of a machine executed in accordance with a first embodiment of the invention, the section of the front part being taken through the lines I-I of FIG- URES 2, 3 and 4;

FIGURE 2 is a cross-section taken through the lines II-II of FIGURE 1;

FIGURE 3 is a cross-section taken through the lines III-III of FIGURE 1;

FIGURE 4 is a cross-section taken through the lines IVIV of FIGURE 1;

FIGURE 5 is a cross-section taken through the lines V-V of FIGURE 1;

FIGURE 6 is a longitudinal sectional view of the front and rear extremities of a tube bending machine executed in accordance with a second embodiment of the invention;

FIGURE 7 is a section taken through the broken lines VIIVII of FIGURE 6;

FIGURE 8 is a frontal view of a pressure plate;

FIGURE 9 is a side elevation view of the plate of FIG- URE 8; and

FIGURE 10 is a detail sectional view on a larger scale, showing the formation of the imprints on the tube wall and the respective positions of the plates producing said lniprints.

The machine executed in accordance with the first embodiment of the invention consists of a base 1 supporting a former comprising two jaws 2 and 3 between which is engaged a tube 4, the lower jaw 2 acting as a support for the rolled wall of tube 4 and the shorter upper jaw 3 being applied against the wall of tube 4 which is subjected to the action of the thrust wheels.

The upper jaw 3 is retained in its operative position by a screw 5 engaging into a cross-piece 25 rigid with the upper part of base 1. In cases where the two jaws 2 and 3 are semi-circular, a clearance must be provided between their contact surfaces by planing the same in such manner as to obtain a slight ovalization of the former once the two jaws have been tightened against each other. Said ovalization can be less than 1 of the tube diameter.

The tube to be rolled 4 is inserted between the jaws 2 and 3 and moves forward slowly from left to right (se FIGURE 1) in response to the action of known means such as, for instance, the thrust of a hydraulic jack (not shown on the drawing).

It will of course be understood that the bent tube 4 is retained to prevent it from rotating about its axis.

Into tube 4 is introduced a rolling head 6 comprising a rolling wheel 7 mounted freely rotatable on the eccentric portion 8 of a shaft 9 which can be revolved bodily by a pinion 10 rigid with said shaft and meshing with a pinion 11which is in turn rigid with a stationary central shaft 12 concentric with the tube to be bent and disposed within a hollow shaft 13. Said hollow shaft is rigid with a pinion 14 meshing with two pinions 15 which are rigid with two spindles 16 provided with eccentric portions 17 about which are freely rotatable thrust wheels 18 (see FIG- URES 1 and 3)v It will of course be obvious that pinion 14 can, if desired, mesh with only one of the two pinions 15, in which case the two pinions 15 must mesh together and rotate in opposite directions.

Externally to shafts 12 and 13, is concentrically disposed the mainshaft 19, one end of which is rigid with rolling head 6 while the other end is rigid with a crank 20 provided with acrank-pin 21 (FIGURES 1 and 5) and oscillated angularly through less than about the common axis of shafts 12,13and 19. The free end of crank 20 is shaped as a fork into which engages the end of a rod 22 pivotally connected to crank-pin 21, the other extremity of rod 22 being provided with an articulation 23 (FIG- URE 5) which describes a full circle resulting from the rotation of a driving pulley 24 the radius of which is less than the center distance between shaft 12 and a crank-pin 21 of crank 20.

The rear extremity of central shaft 12 is so immobilized by a key in the upright 26 of base 1 that, when maximum rolling takes place, the eccentric 8 be oriented toward G that generating line of the tube which is to form the outer arc of the bent tube.

The rear extremity of hollow shaft 15 is provided with a plate 27 and a hand-lever 28 adapted to be latched in a preset angular position relative to shaft 19 by means of a pin 29 adapted to engage in one of holes 30 provided in plate 27. Said holes 39 correspond to the different positions which can be assumed by the eccentrics 17, accord ing to the diameter of the tube to be rolled and the bending radius to be obtained.

The machine is further provided with a system for heating the tube wall to be compressed, i.e. the wall on the inner are side of the bend. Said system could consist, for instance, of a distributor bank '31 comprising a plurality of nozzles 32 operating as oxyacetylene torches and ringing the tube portion to be heated in a plane roughly perpendicular to the axis of tube 4. The heating could alternatively be effected by a single oxyacetylene torch nozzle offset through 180 relative to the rolling wheel and possessed of an oscillating motion of identical amplitude as that of the wheel. It will of course be understood, however, that any convenient alternative heating means can be resorted to.

By reason of the relatively rapid advance of the bent tube, heating of the rolled wall through conduction need not be feared, but on the other hand the rolling head 6 may be heated by radiation. To avoid heating by infrared rays, this invention provides for a protective screen 33, preferably made of asbestos, to shield the extremity of rolling head 6.

It is to be noted that the rolling depth can be adjusted simply by tighten-ing down the screw retaining upper jaw 3, provided however that the tube former be slightly ovalized. Under such conditions, the compound comprising eccentric 8, pinions and 11 and stationary central shaft 12 is no longer indispensable for work not requiring a high degree of accuracy and wherein slight ovalization of tube 4 is no drawback. When such is the case, wheel 7 can be freely rotatable about a non-eccentric shaft.

In contradistinction, when it is necessary to obtain a perfectly round tube section free from ovalization, the compound consisting of parts 8, 9, 1G, 11 and 12 gives better results than an ovalized former.

The two devices which control adjustment of the rolling depth can be used jointly, as will be clear from the description of the machine submitted by way of example but not of limitation.

Although experience has shown that an oscillating movement of the rolling head' is, more, rational than a continuous rotary motion, since it obviates the twisting effect resultingfrom the displacement of metal in one direction only-which, to be overcome in the case of machines with a continuously rotating rolling head, required the provision of a special, complex and costly tube straightening device calling for a highly skilled operatorit will be manifest that the non-rolled portion of the tube can also be heated when the rolling head 6 revolves continuously, provided that the rolled portion is not too large and preferably'less than 180.

The device according to this invention operates in the following manner: the tube to be bent 4' is engaged between the jaws 2 and 3 of base 1 in such manner'that rolling head 6 locates within the tube, after which the tube end inside. the machine is secured. tov the carriage (not shown) of the bending machine-toprevent it fromro-tating about its axis during the travel motionofthecarriage. laws 2 and 3- are then tightened down by means of screw 5 soas to obtain a slight ovalization of tube, 4.

The motor. driving pulley 2,4 is then startedv up, and said pulley sets rod 22 in motion, which. in turn causes crank to oscillate through a. circular arc (of. 150 for example, according to a preferred embodiment-see FIG- URE 5) about the central shaft 12 common to crank. 20 and rolling head 6. Since crank 20 is rigid with mainshaft 19 and shaft 13crank 20 being coupled to plate 27 by a pin 29said shafts 19 and 13 will likewise be set oscillating and Will in turn cause rolling head 6 to be oscillated about its axis through an angle identical to the angular displacement of crank Zil (i.e. in the example illustrated) and this angle of oscillation will be equally divided on either side of the vertical plane passing through the axis of the tube to be bent 4. During the oscillating movement of rolling head 6, the tube is thrust toward the right of FIGURE 1, either by a hydraulic jack, by a feedscrew driven by pulley 24, or by any other convenient means.

At the same time as the rolling mechanism is started up, the heating bank 31 is ignited and raises the wall of the non-rolled portion of the tube to a temperature at which the metal becomes ductile and can be worked under compression without difficulty.

For the tube bend to be uniform, the rolling depth must be at a maximum when rolling wheel 7 is at its lowermost point and at a minimum, or null, at the two extreme points of its travel. This can be achieved by slightly ovalizing the. tube and also by means of the eccentric 8 forming part of the compound consisting of stationary shaft 12, pinion '11 rigid therewith, and pinion 10 rigid with shaft 9 which. supports the rolling wheel 7 rotating freely about said eccentric. When rolling head 6 oscillates about its axis, shaft 9 describes a circular are about the axis of rolling head 6 and pinion -10 revolves about the stationary pinion 11 of stationary shaft 12 after the fashion. of a planet gear, so that even if the tube to be rolled were not ovalized, maximum rolling would be" obtained when the rolling wheel is at its lowermost point and minimum rolling when said. wheel reaches the limit of its travel since, at that moment, the revolving motion of eccentric 8 fetches wheel 7 close to the axis of the tube to be rolled, whereas when said wheel 7 is. at itslowermost point it isspaced at a maximum from the tube axis, which corresponds to maximum rolling depth.

The rolling depth can be increased by screwing down the clamping screw 5.

Furthermore, suitable adjustmentof the thrust wheels 18 by angularly presetting the eccentrics 17 allows for adapting the machine to the bending of tubes of different diameters and for varying the bending radius of the tubes. This adjustmentis made by means of plate 27, through the medium of the hand-lever 28 which is rigid with hollow' shaft 1-3 and located at the rear of the machine. Plate 27 is displaceable relative to crank 20' through a circular arc, while holes 30 drilled into it make it possible to lock hand-lever 28 in the desired angular position relative to shaft 191 Hollow shaft 13 supports a pinion 14 which rotates when handl'ever 28 is operated. Said pinion 14 rotates the pi-nions 15 supported on spindles 16 (see FIGURE 4), which spindles in turn rotate about their respective axes, together with the eccentric portions 17, thereby increasing or reducing the eccentricity of thrust wheels 18 by moving them away from or toward each other.

The machine executed in accordance with the second embodiment referred to hereinbefore consists of" a base 40 comprising a former composed of two semi-circular jaws 41 and 42, between which is longitudinally slid'able a tube tobe bent 43. Into-tube 43 is introduced an expandable mandrel 44 the upper pressure wall of' which lags behind the lower pressure wall, the latter terminating at the point of internal curvature of the. bent tube. Expandable mandrel 44' is provided" with an axial bore into which engages a central rod 45 provided with a conical portion 46 adapted to bulge the mandrel by spreading apart its three sections 47-48-49, so as to exactly match the diameter of the mandrel to the inner diameter of the tube to be bent.

A portion of base 40 located immediately beneath the lower extremity of mandrel 44 embodies two recesses serving as housings for members 50 and 51 which are designed to compress the tube wall so as to thin it down and lengthen it. These members are shaped as plates the upper portions of which embody roughly semi-circular hollows 52 encompassing 160 for instance and matching the diameter of the tube to be bent. The profile of the semi-circular hollow of plate 50 is rounded to facilitate its introduction into the tube wall, while the profile of the semi-circular hollow of plate 51 is flat to allow equalizing of the outer tube surface, which is initially striped by the first plate 50.

The upward displacement of plates 50 and 51 is controlled by push-rods 53 and 54, while their downward displacement is insured by flat springs 55 and 56.

The upper and lower extremities of said push-rods are rounded so that their upper extremities can pivot inside the lower concave extremities of plates 50 and 51, and their lower extremities in corresponding cavities embodied in arms 57 and 58 which are oscillatable about pins 59 and 60 respectively. The oscillatory motion of oscillating arms 57 and 58 is caused by the rotation of shafts 61 and 62, of which the eccentric portions 63 and 64 are so off-set by a certain angle that the push rod 54 operate positively on plate 51 as soon as compression of the tube by plate 50 is completed.

The vertical location of shafts 61 and 62 is adjusted by angular displacement of bearings 65, the inner bores receiving shafts 61 and 62 of which are eccentric with respect to the outer contours of said bearings. Angular displacement of bearings 65 is accomplished by adjustment frames 66 which are interconnected by a link 67 the extremities of which are pivotally connected to pins 68. The assembly can be immobilized in a preset position, according to the bending radius to be obtained.

In FIGURES 6 and 7 the adjustment frames 66 are shown in the midway position, but when the accentric bearings 65 are rotated through 45 in one direction or the other, this gives a position providing maximum introduction of plates 50 and 51 into the metal of the tubecorresponding to minimum bending radius-or else a position providing null plate introduction into the metal, i.e. no bending. These extreme positions of bearings 65 correspond to the positions of the bearing adjustment frames shown in dotted lines, when the hinge pins 68 move into position 68' and 68" respectively.

This arrangement permits adjustment of the bending radius while the machine is operating, as well as modification of this radius as desired. Manifestly, the system can be immobilized in a preset position by any convenient means whatsoever (not shown).

At one extremity, the shafts 61 and 62 mount pinions 69 and 70 respectively, which mesh together, thereby causing said shafts 61 and 62 to rotate in opposite directions. The system is set in rotation by a pulley 71 fixed to the opposite extremity of one of the two shafts.

The base 40 further comprises a rack 72 which is movable longtiudinally in slideways provided for the purpose in uprights 73 and 74 of base 40. The reciprocating motion of the rack is controlled by the eccentric 63, and the distance between two successive cogs of the rack must be less than the eccentricity of eccentric 63 relative to shaft 61, so that each revolution of eccentric 63 causes the rack to move through one cog, thereby enabling the tip of a pawl 75 loaded by a flat spring 76 to engage with a cog on rack 72.

Said pawl 75 is pivotally mounted on a pin 77 rigid with a plug which is bored axially and inserted into the rear end of the tube to be bent 43.

This device permits engagement with a cog on rack 72 on each revolution of eccentric 63, whereby the reciprocating motion of the rack causes the tube to be bent to be fed along, through the medium of plug 78, pawl 75 and rack 72. As stated precedingly pawl 75 is urged against the rack by a spring 76.

The upper jaw 41 is maintained in pressure contact 5 with the tube to be bent 43 by a screw 79 equipped with a handwheel 80. i

The tube wall is heated over the inner arc of the bend by means of the nozzle 81, as described hereinbefore with reference to the first embodiment of this invention.

The expandable mandrel 44 is extended rearwardly by a hollow shaft 82 of which the threaded extremity 83 is retained in the upright 73 of base 40 by a nut 84.

Adjustment of the diameter of expandable mandrel 44 is accomplished by the pull exerted on the rod 45 by a nut 85 screwed onto the threaded end 86 of said rod 45.

The front extremity of mandrel 44 as well as the cone 46 are shielded against the heat produced by the infrared rays by an asbestos screen 87 secured to the mandrel by a screw 88.

This machine functions in the following manner: the machine is halted when the angular position of eccentrics 63 and 64 allows plates 50 and 51 to locate in their lowermost position. The tube to be bent 43 is then placed upon the lower jaw 42 and mandrel 44 is inserted into the tube. Cone 46 is pushed forward in order to reduce the diameter of mandrel 44 and facilitate its insertion into the tube to be bent 43. Rod 45 is next pulled rearwardly, by screwing up nut 85 and thereby causing cone 46 to expand mandrel 44 until the diameter of same is equal to the inner diameter of the tube to be bent.

The plug 78 is then inserted into the opposite end of ltube 43, taking care to insure that the tip of pawl 75 engages with a cog of rack 72. Screw 79 is then tightened by means of the handwheel 80, and the angular position of bearings 65 is determined according to the bending radius to be obtained.

Once this has been done, the machine is set in rotation by means of pulley 71 and the drive motor (not shown on the drawing).

At each revolution of pulley 71, the eccentric 63 causes the semi-circular hollow 52 on plate 50 to penetrate into the outer tube wall, to a depth determined by the adustment of bearings 65. The hollow 52 of plate 50 then begins to descend. Plate 51, operation of which is outphased by one-eighth or one-sixth of a revolution, say, relative to operation of plate 50, compresses the tube metal by crushing the excrescence produced between the two successive hollows impressed by plate 50, thereby allowing for smoothing of the surface first striped by plate 50.

During the first half-revolution of pulley 71, the semicircular hollows 52 of the two plates 50 and 51 are in contact with the outer wall of the tube. Said tube cannot move forward, but rack 72 moves back to the left and, before the end of its travel, the tip of pawl 75 drops into another notch on the rack, which moves from left to right during the second half-revolution of the pulley, carrying the tube with it toward the front through the medium of plug 78.

It will of course be understood that the two plates 50 and 51 are not in contact with the wall of the tube when the latter is moving, since eccentrics 63 and 64 are turned downwardly.

At the same time, the nozzles 81 of the oxyacetylene torch are ignited to make the metal ductile over the side corresponding to the inner arc of the bend, and also to facilitate its compression. This operation is identical with that described with reference to the first embodiment.

The machine described hereinabove can be used for quantity production. However, for the benefit of concerns undertaking isolated bending operations involving one or two units for instance, it is possible to design a simplified tool along similar lines to replace the machine. Such a tool could consist of a plate with a semi-circular hollow engaging into a semi-cylindrical jaw, the tube to be bent being caused to bear against another jaw. The mandrel would be inserted into the tube in the same way as in the machine described precedingly. In order to simplify construction, however, said tool need comprise no mechanical component or motor as that used to operate the machine. The semi-circular imprints impressed upon that sur faceof the tube which is to form the outer arc could be made by means of a hammer, with which the plate would be struck repeatedly to cause it to penetrate into the metal and flatten it. The plate could be restored to its initial position by means of a return spring, while the tube would be fed through the former manually either directly or by means of a hand-operated mechanical device, with the aid for instance of a rack, between two successive hammer blows. At the same time, the oxyacetylene torch would heat the face designed to form the inner arc of the bend. Obviously, a pneumatic, electric, or mechanical trip-hammer could be substituted for ordinary hammer blows.

It will manifest that although this simplified method is not suitable for batch production, it could nevertheless prove useful for bending single tubes.

The chief advantage of the method of this invention resides in the possibility of bending all the tubes of same diameter using a same tool means corresponding to the tube diameter. In addition, it is possible to obtain any desired bending radius ranging from twice the tube diameter'to infinity.

Iclaim:

Method of bending tubes consisting in cold thinning the wall of the tube on the side thereof on the outer arc of curvature, o'vera 160 portion of the tuhe'periphery providing an elongation thereof, heating the opposite side of the tube periphery on an arc of 160 at a temperatureof I000 C. whereby a small width on both sides of the tube are neither thinned down not heated on the transverse plan of thinning during the thinning of the tube, and said coldthinning of the tube being carried out at regular intervals on the tube during longitudinal displacement thereof intwosuccessive periods by pressing semi-circular grooves in the tube in the first period and thereafter compressing the semi-circular excrescences on the tube produced between two successive grooves during the secend period for smoothing the external surface of the tube.

References Cited UNITED STATES PATENTS 1,996,838 4/ 1935 Snell 29157 X 2,428,825 10/1947 Arnoldy 29157 2,433,055 12/1947 Linden et al. 15332 X 2,901,930 9/ 1959 Wilman 153--32 X 2,966,197 12/ 1960 Huet. 2,983,995 5/1961 Gresse 29-157.6 3,029,668 4/1962 Wilman 11 3,229,489 1/ 1966 Huet.

FOREIGN PATENTS 194,679 1/195'8 Austria.

1,155,972 12/1957 France.

CHARLIE T. MOON, Primary Examiner.

WHIT MORE A. WILTZ, Examiner.

I. D. HOBART, P. M. COHEN, Assistant Examiners. 

